7 Essential Signs for When to Harvest Onions

Knowing when to harvest onions is crucial for taste and storage success. If you pull them too soon, you will have tiny bulbs that won't keep. If you wait too long, rot occurs, and your hard work is wasted. Timing is crucial for maintaining the quality of your crop.

I'll describe the simple signs to watch for. Tops are the green leaves, and necks are the connections that connect the leaves to the bulb. Curing is the proper drying of the onion. All of these terms will serve to identify a perfect time for harvest, and prevent confusion with the timing discussed in the previous section.

I figured this out the hard way, my first growing season. I had early-harvested onions that dried out in storage, and the late-harvested onions went mushy. Now, I talk with gardeners about watching the plant's cues. The onions tell you exactly when it's time.

Monitor for neck softening as your first indicator of harvest readiness. Neck softening denotes that onions have completed the transition of carbohydrates into the bulb. To check for neck softening, gently squeeze the spot where leaves meet the bulb. When the necks feel soft, the energy transfer is complete. If the necks think hard, then the onions need more time to grow.

Papery outer skins safeguard onions from moisture loss in storage. At harvest time, it is easy to discern when the skins are ready, as they crackle like dried-up leaves when touched. I learned this daily, partly out of necessity, as we approached harvest time. Protective layers form only when onions truly reach full maturity.

Ensure the youngest leaf adjacent to the bulb base is completely dry. Any green leaf or moisture here would cause rotting to occur later. I once lost an entire crop because I ignored this sign. Now I teach that gardeners need to be aware of this sign as well.

Sweet onions, such as Vidalia, can grow to 3-4 inches in diameter before being harvested. However, storage varieties such as Copra need to grow to more like 4-5 inches. The size can vary by onion type, so it's important to know your specific cultivar. Having a variety of tags can avoid guessing.

When loosening the soil, keep your garden fork 6 inches from the bulbs. This avoids piercing and ruining the onions, as I learned the hard way with my first planting. I learned not to use a garden fork near the crop. Insert the fork into the soil based on my crop. Place the fork straight down in the ground, and gently lever up on the handle while keeping the fork out.

You should only harvest when the soil is bone dry, which helps to prevent any diseases. Fungal spores responsible for sour skin and black mold survive in moist soil. For that reason, stop watering 7-14 days before your harvest. To check, squeeze a handful of soil in your hand. If the soil clumps, it is still moist. If the soil crumbles, it is dry enough.

Try to plan your harvest for cool morning hours when temperatures are below 75°F. The heat causes sunscald, which can harm the protective skin. I begin harvesting at dawn in the summer. The morning dew has dried up, but the temperature remains friendly to the plant.

Gently pull the onions while applying an even upward pressure. Avoid yanking or twisting that separates the green tops. Pulling the onions strongly leaves an open area for rot bacteria to enter. While pulling, you need to support the bulb. Damaging the onion will cause it to spoil quickly in storage.

For field curing, I place onions in single rows on sunny days between 75°F and 90°F. The tops should cover the bulb for protection. I do this for 2-4 days and check daily. For indoor curing, I use mesh trays at a consistent temperature of 60% humidity with fan circulation.

You can use your fingers to feel for neck tightness. A papery tight neck will help block bacteria from entering. A soft neck will take longer to dry. I've lost bulbs to rot before I learned that this barrier is the most important aspect in storage success. Tight necks will self-seal.

Using sterilized shears, trim roots flush to the bulb base. Don't leave stubs that could regrow. Cutting cleanly is important to stop mold from growing. I carry alcohol wipes to clean tools between plants. This simple step can add months to storage life.

Check bulbs for any flaws before storing. Discard any bruised, thick-necked, or green-spotted bulbs. Damaged bulbs produce ethylene gas, which can cause spoilage in other bulbs. I sort onions using bright light to check for any defects. One bad onion can spoil an entire bin of onions.

Your storage temperature should be between 32°F and 36°F to prevent sprouting at temperatures above 40°F and to prevent frozen damage at temperatures below 32°F. I started using thermostat alarms after onions were affected by temperature fluctuations. The goal is to keep the bulb firm for 6-12 months of storage.

Hygrometers help monitor humidity in your bulbs, so you want to keep it to 60% or less with the use of dehumidifiers. Higher humidity leads to moldy, rotting bulbs, while low humidity results in dried-out bulbs. I check mine weekly in winter when the air indoors is dry.

Opt for tray storage vs. braiding for excellent air flow. Braids can look cute; however, they can trap moisture between the strands. Mesh trays with slats allow air flow around the bulbs. I've converted to trays after I found mold on my braided onions.

Keep onions away from ethylene-producing fruits like apples and potatoes. Store them at least 3 feet apart. Ethylene causes onions to sprout prematurely, and onions can damage the taste of nearby produce. I use different rooms for my fruits and onions now.

Never bend green tops, to try to hasten harvesting. Doing this eliminates leaves carrying carbohydrates into bulbs, and I found, alongside other intermediate plants, that doing this yielded onions that were 30% their normal size. You want the tops to fall over on their own, maximizing energy transfer into the bulbs.

Cutting tops before curing causes bacterial rot. I have learned from losing around half of my crop. Cutting too soon creates open necks. Always wait until you feel that your necks are papery tight before trimming tops to one inch above the bulbs.

Washing onions traps moisture between the layers, which can cause black mold. Dry brushing is a safe alternative. I ruined my first onion harvest by using too much water. Now I teach gardeners about this critical and simple moisture control method for storage success.

Harvesting in wet soils spreads fungal spores and bruises bulbs. Be patient and wait until conditions are dry. Mud compaction caused rot in my earlier crops. Now I check the moisture level in the soil for several days before harvesting.

Getting harvesting timing right is what determines how long your onions last in storage. During my first year, I harvested too early and lost bulbs to rot. The right timing grants you months of kitchen-ready onions with no waste. It makes all the difference.

*Neck tightness* does provide a natural barrier against rot bacteria. You can check for tightness by rolling the neck between your fingers. If it feels papery tight, it is safe to store. It took me years to figure out that the barrier does hold up and saved a whole crop from loss. Loose necks will always mean trouble.

Maintain curing temperatures accurately between 75-90°F for protective skin formation. This layer prevents moisture damage. I check thermometer readings twice daily. Room temperature warms much faster to build defenses than it could ever dry quickly.

For storage types, select storage varieties like Copra. Sweet onions are the kind you want to eat quickly. Determine the right types for your purpose. I grow both types currently for different purposes. Choosing your varieties to plan allows you to have onions all year.